The RNA polymerase I transcription machinery

摘要

The rRNAs constitute the catalytic and structural components of the ribosome,the protein synthesis machinery of cells.The level of rRNA synthesis,mediated by Pol I (RNA polymerase I),therefore has a major impact on the life and destiny of a cell.In order to elucidate how cells achieve the stringent control of Pol I transcription,matching the supply of rRNA to demand under different cellular growth conditions,it is essential to understand the components and mechanics of the Pol I transcription machinery.In this review,we discuss:(i) the molecular composition and functions of the Pol I enzyme complex and the two main Pol I transcription factors,SL1 (selectivity factor 1) and UBF (upstream binding factor);(ii) the interplay between these factors during pre-initiation complex formation at the rDNA promoter in mammalian cells;and (iii) the cellular control of the Pol I transcription machinery.